50 000 DEM of Chaohu Basin was selected as base data for this study. The extracting accuracy of hydrologic characteristics was evaluated individually for five DEM generalization methods(nearest neigh bor, bilinear interpolation, cubic convolution, structured generalization, quadric surface fitting) based on three parameters including matching error of river networks, matching error of sub-watershed and gully den-sity. The results show that the extracting accuracy of hydrological structure information based on the low resolution DEM followed a descending order of the five terrain generalization methods as： quadric surface fit-ting＞structured generalization＞cubic convolution＞bilinearinterpolation＞nearest neighbor, with very subtle accuracy difference.